I shall continue to characterize glycoproteins synthesized by the developing heart at different times of development and compare them for ontogenic differences. The injection of specific hydrolytic enzymes into the cardiac jelly will continue in an effort to determine the role of specific components on heart morphogenesis. An attempt will be made to visualize, by means of back-scatter SEM techniques, the orientation of developing myofibrils within the myocardium at different developmental stages. By this means we hope to determine the relationships between fibril assembly and alignment to cell and heart shape. BIBLIOGRAPHIC REFERENCES: Manasek, F.J.: Heart Development: Interactions involved in cardiac morphogenesis. In: Cell Surface Interactions in Embryogenesis (Eds.: G. Poste and G. Nicholson) Elsevier, Amsterdam, (In press) 1976. Manasek, F.J.: Glycoprotein synthesis and tissue interactions during establishment of the functional embryonic chick heart. J. Mol. Cell. Cardiol. (In press) 1976.